Method for producing single crystal and a method for producing annealed wafer

Abstract

The present invention is a method for producing a single crystal that is a multi-pulling method for pulling a plurality of single crystals from a raw material melt in a same crucible in a chamber by a Czochralski method, comprising steps of: pulling a single crystal from a raw material melt ; then additionally charging polycrystalline raw material in a residual raw material melt without turning off power of a heater, and melting the polycrystalline raw material; then pulling a next single crystal; and repeating the steps and thereby pulling the plurality of single crystals.

1. A method for producing a single crystal that is a multi-pulling method for pulling a plurality of single crystals from a raw material melt in a same crucible in a chamber by a Czochralski method, comprising steps of:
 pulling a single crystal from a raw material melt; then 
 additionally charging polycrystalline raw material in a residual raw material melt without turning off power of a heater, and melting the polycrystalline raw material; then 
 pulling a next single crystal; and 
 repeating the steps and thereby pulling the plurality of single crystals; 
 wherein in a case of setting a ratio of a pulling rate V and crystal temperature gradient G near a solid-liquid interface along a pulling axis direction when a straight body of the single crystal is grown to be V/G, in order to control the V/G of each of the single crystals to be pulled to a predetermined value, any one or more of pulling conditions of at least, the pulling rate V, flow amount of an inert gas introduced into the chamber, pressure in the chamber, and distance between a melt surface of the raw material melt and a heat-shielding member disposed oppositely to the raw material melt surface in the chamber, is preliminarily modified according to an elapsed time from beginning of operation, before initiating pulling each next single crystal but after pulling of an immediately preceding crystal; and thereby 
 the single crystal having a desired defect region is grown. 
 
     
     
       2. The method for producing a single crystal according to  claim 1 , wherein in a case of pulling at least two or more single crystals having a same variety out of the plurality of single crystals to be pulled, in order that the V/G is a same predetermined value, the pulling condition(s) of each of the single crystals is/are preliminarily modified according to what time of pulling the single crystal is, before initiating pulling the single crystal. 
     
     
       3. The method for producing a single crystal according to  claim 1 , wherein the modification of the pulling condition(s) is performed by
 preliminarily preparing a plurality of patterns of the respective pulling conditions under the elapsed time and 
 selecting the most appropriate pattern of the pulling condition for the single crystal to be pulled according to the elapsed time. 
 
     
     
       4. The method for producing a single crystal according to  claim 2 , wherein the modification of the pulling condition(s) is performed by
 preliminarily preparing a plurality of patterns of the respective pulling conditions under the elapsed time and 
 selecting the most appropriate pattern of the pulling condition for the single crystal to be pulled according to the elapsed time. 
 
     
     
       5. The method for producing a single crystal according to  claim 1 , wherein a silicon single crystal that is the single crystal doped with nitrogen is pulled. 
     
     
       6. The method for producing a single crystal according to  claim 2 , wherein a silicon single crystal that is the single crystal doped with nitrogen is pulled. 
     
     
       7. The method for producing a single crystal according to  claim 3 , wherein a silicon single crystal that is the single crystal doped with nitrogen is pulled. 
     
     
       8. The method for producing a single crystal according to  claim 4 , wherein a silicon single crystal that is the single crystal doped with nitrogen is pulled. 
     
     
       9. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 1 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C. ˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       10. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 2 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C.˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       11. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 3 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C.˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       12. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 4 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C.˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       13. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 5 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C.˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       14. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 6 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C.˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       15. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 7 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C.˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       16. A method for producing an annealed wafer, comprising steps of:
 producing a silicon single crystal according to  claim 8 ; 
 slicing a silicon wafer from the silicon single crystal; 
 subjecting the silicon wafer to a heat treatment at 1100° C.˜1400° C. for 5 min ˜600 min under a non-oxidizing atmosphere of hydrogen, argon, or a mixed gas thereof; and thereby producing the annealed wafer. 
 
     
     
       17. The method for producing an annealed wafer according to  claim 9 , wherein
 an average density of surface-near defects having sizes of 20 nm or more in a surface vicinity from each of surfaces of the annealed wafers to a depth of 5 μm is 20/cm 2  or less, and 
 variations of densities of surface-near defects having sizes of 20 nm or more in a surface vicinity from each of surfaces of the annealed wafers to a depth of 5 μm along its crystal axis direction is 100% or less of an average of the densities. 
 
     
     
       18. The method for producing an annealed wafer according to  claim 16 , wherein
 an average density of surface-near defects having sizes of 20 nm or more in a surface vicinity from each of surfaces of the annealed wafers to a depth of 5 μm is 20/cm 2  or less, and 
 variations of densities of surface-near defects having sizes of 20 nm or more in a surface vicinity from each of surfaces of the annealed wafers to a depth of 5 μm along its crystal axis direction is 100% or less of an average of the densities.